Since light-emitting diodes came into practice, lighting equipment using lamps composed of light-emitting diodes has displayed special advantages over the existing fluorescent lamps, incandescent lamps and the like, these advantages being their longer service life and lower energy consumption.
Lighting devices with light-emitting diodes (LEDs) used as searchlights or traffic lights are described in detail in the RF patents such as No. 2123633, No. 2151473, No. 2153623, No. 2202731, No. 2227245, No. 2244870, No. 2248499, etc. The purpose thereof is to illuminate remote objects, to be used in circular scanning systems and lighting devices which do not require the creation of a maximum level of illumination within a working zone or maintaining a constant diameter of the light field.
However, until now LEDs have not found broad use in surgical lighting devices, which are required to ensure a shadowless effect and a high illuminating efficiency through high illuminance and uniform distribution of luminous flux across the working zone. The luminous flux in surgical lighting devices is created by combining the luminous fluxes emitted by individual light-optical modules, which occurs at a distance of 0.7 m to 1.4 m from the body. Inside the working zone, a maximum level of illumination is created and a constant diameter of the light field is maintained. Moreover, the possibility of adjusting the diameter of the light field should be provided for. To this end, surgical lights are provided with light field control devices which represent, in general, rotary mechanical devices.
Known is a surgical light with a light field adjusting mechanism made in the form of a rotary mirror reflecting the light beam from a source of light (Lighting device type BH-500 manufactured by FAMED, Poland).
This known lighting device is provided with a light field adjusting mechanism which is not sufficiently effective because of low synchronization of rays, use of extra reflecting surface, and also it has large dimensions.
Known is a surgical lighting device in which the adjustment of the illumination system is performed by moving the lamp relative to the reflector (surgical light CH-6; certificate 66-00-00ΠC).
The known lighting device may only adjust the size of a light spot featuring small depth, this lighting device also has large overall dimensions.
Also known is a surgical light with light emission control comprising light optical elements in the form of halogen lamps secured in the body and a light field adjustment mechanism, including a supporting rod mounted on the main axis of the lighting system, said supporting rod having a split spherical joint with six degrees of freedom in the upper part thereof, a means for rotating the light-optical elements in the form of a multiple thread cam located under the spherical joint and interacting with the vertical levers of the brackets of the light-optical elements interacting with the adjusting pins (patent of the Russian Federation No. 2149309, IPC F21V 14/02, F21V21/29, F21W131:205, published on May 20, 2000).
In the known technical solution, light emission control is performed by mechanical means ensuring the rotation of the light optical elements having a complex construction and large overall dimensions, reliability of which is reduced as the mechanical units wear out.
Technically, the most close to the claimed device is the surgical light comprising light-optical elements affixed to the body and hinged to each other, and light field control by mechanical means (application for EP No. 1568935, IPC F21S 8/00, F21S 2/00, published on Aug. 31, 2005).
The known lighting device features high illumination effectiveness. However, light emission control in the known lighting device is performed by mechanical means which ensure the rotation of the light-optical elements relative to each other, reliability of which is reduced as the mechanical parts wear out.